Airfoil



Patented Mar. 22, 1932 UNITED sm 'rrsf r 1,s50,954, v

PATENT elem-e1;

Tenn nnnnncir, or BALTIIOBE-IABYLAND- Amen,

application and January 22, 1930. serial no. 422,639.

'This invention relates to improvements in airplanes-and more particularly has reference to la method'and means for increasing.

the liftfactor of airfoils. A 5 A considerable effort has been expended to increase the lift effect on airplanewings as its desirability has-long been recognized. At

I the present, the advantage to .be gained from a short distance take-ofl' and -a relatively low 1 landingspeed, so that the plane may land in small spaces are'still being sought. Methods proposed to secure thesefadvantages have beenan increased wing camber and an increased wing area. However, these expedie ents are limited by the size of the wings which are capable of being-"used; Other methods have proposed a wing construction which. allows the camber and the Wing area to be altered at will. While this latter type 29 of construction is correct in' theory,lit is I nevertheless-impractical becauseofthe many mechanical parts required by it. e

4 Besides these practices mentioned above,

7 attempts have been made to increase the lift.- 33 ing power of an airfoil by increasing the air current velocity over the top surface. Along these-lines the'slotted wing has had consid'erable success but as yet it is not suitable in all instances. Also among this latter type of methods and constructions now in present An equally important object er the invention is to create a" current of air which is dithereoff Another objectof the invention is to mflfe use of the interior'surfaces of an airfoil to increase the lifting effect.

cordance with the present invention.

into efiect which lack the inherentdefectsof rected around the airfoil from its bottom surface upwardly and over the top surface Yet another object of the invention is to circulate a. current ofiair within the interior of an airfoil, the air current entering and leaving the airfoil at its bottom-surfacee In addition ,to the above objects the present invention contemplates the construction of airplane Wings so that :an airplane may land in small spaces, at relatively low speeds and with a maximum factor of safety.

Stilt another object of the invention is the .Pl'OVlSlOIl of an airfoil havinga plurality of rotatable v'ane elements mounted within openings formed in the bottom surface of the air-- foil.

A A further-object of the inventionisthe pro- 6 5;

vision of a rotatable-member mounted within an opening formed in the, bottom surface of an airfoil, and means mounted upon an ai'rplane, with which the airfoil is associated; for rotating the member. e v r Yet a further object of the invention is the provision'of an auxiliary wing adapted to be mounted below the main wing of an airplane, the auxiliary wing being constructed in ac- With these and other objects in view, which.

may be incident to my improvements, the invention consists in the parts and combinations tobe hereinafter set forth and 'elaimed,'with' the understanding that the several necessary $9 elements comprising" my invention may be' varied in construction, proportions and. ar-" rangement without departing from the spirit andscope of theIappended claims.

The present invention comprehendsametb 3 i 0d and apparatus for increasing the lift 'fac-- 1- tor of airfoils. One method of practically effecting theconcept of'the invention is the provision of an airfoil having an opening 9" formed in its lower surface and means upon the plane with which the airfoil'isassociated for'rotatingr vane mechanism positioned within the openings;

, In order to make my mventiori more clearly e understood, I have shown, in the accompanying drawings, means for carrying the same into practical effect without limiting the improvements in'their useful applications to the particular constructions whieh, for'the pm}- the vane structure embodied therein.

Figure 3 is a cross sectional elevation along the line 33 of Figure 1 and shows the manner of mounting a vane element.

Figure 4 is a sectional elevation view of the vane elements along the line 4-4 of Figure 1.

There is shown in Figure 1 an airplane having a fuselage 1 and a wing or airfoil 2. The airfoil 2 is provided with the usual ailerons 3 while the tail of the fuselage has the conventional elevators 4 and stabilizer 5. A suitable tail skid 6 and landing gear 7 are also shown.

As may be observed from Figures 1 and 3 the wing 2 is of any suitable airfoil section and has formed upon its under surface a plurality of openings 9. The openings 9 are formed in each semi-span of the wing and have positioned therein rotatable vane elements 10 which are fixed to the shafts 11. The shafts 11, as shown in Figure 4 are rotatably mounted in suitable bearings 12 which may be fixed to the ribs 13 of the airfoil. However, any other suitable bearing support for the shafts 11 may be employed. This construction, it will be observed, provides a set of vane elements on each side of the fuselage or on each semi-span.

For the purpose of providing a commercial structure, the openings have been shown as formedwithin a plate like structure 9'. A plate 9 is mounted upon each semi-span of the airfoil and is covered with the usual surfacin material. It will be appreciated that by this feature the plate may be made especially and set in or recessed into the lower wing surface so that it is flush thereto. Of course, if it is desired the openings 9 may be out directly into the lower wing surface and the plate 9 dispensed with.

It is to be noted that each vane element is of a size substantially equal to an opening 9, and is so designed that it may freely rotate within the opening. Likewise it should be noted that each vane element is constructed in such a manner that when in position to close its opening, its bottom surface will be substantially flush with the bottom surface of the airfoil.

For rotating the vanes a suitable power unit 14. shown by the dotted lines in Figure 1, is connected to the shafts 11. In order to prevent the drawings from becoming highly complicated by reason of unnecessary detail, the shafts 11, provided for each set of verse axis of the airfoil.

vane elements, have been shown as directly connected to the power unit 14. It is to be understood, however, that a suitable clutch arrangement between each of these shafts and the power source may be employed so.

that either or both shafts 11 may be uncoupled from the power unit and the lattermay be actuated without rotating the vane elements. Also it is to be understood that although I have shown a separate power unit for'rotating the vane elements, by suitable connections the shafts 11 could be engaged with the motor driving the propeller 8 and the separate power source 14 eliminated.

While the-construction details have shown each set of vane elements as being positioned upon the wing so that the axis of the shaft upon which the vanes are mounted is parallel to the longitudinal axis of the airfoil, it will be appreciated that each set of vanes may be so positioned that the axis of its shaft is perpendicular to the longitudinal axis of the airfoil or it may be angularly disposed thereto. In these latter events, each set of vane elements could be driven by a separate power unit or by means of suitable gearing could be connected to a centralized unit, such as that shown at 14, or to the prime mover rotating the propeller.

As it will hereinafter become apparent the invention is in no ways limited to the number of vane elements, it being within the scope of the invention to employ one such vane element of greatly enlarged area on each semiwing span. Neither are the vane elements limited in shape, area or their position with respect to either the longitudinal or the trans- For instance the vanes or impellers may be of any desired shape, circular, square, etc, and may be located in any portion of the wing structure, in any position depending upon the type of airplane and the results to be obtained. Moreover, while I have shown the invention as embodied in a monoplane, it will be appreciated by those skilled in the art, that it may be embodied in other types of plane as well, for example a biplane or tri lane. It will also become apparent that the nvention is not limited to any particular type of airfoil section, as it may be.equally well employed with any airfoil section design.

It has been pointed out as an object of the invention to provide a method and means for increasing the lifting power of airfoils, this increased lift being of particular advantage in allowing a short distance takeoff and a relatively low landing s eed and small space for landing a plane. s is well known. the creation of lift in an airfoil is due to the pressure differential existing between the pressure upon the upper surface of the airfoil and the pressure upon its lowsurface is negative in value, or a suction effect, whilethatupon the lower surface is positive with respect to the atmospheric pressure.- 1

The best explanation of the values of these areas of high and low pressure about the air-- foil may be obtained lay-the applicatiton of some of the theorems of hydro-dynamics, particularly Bernoullis. As an airfoil' is moved forwardlythere is always air ahead of it which has not been disturbed by the passage of the airfoil. This air is referred to as the air stream and as it reaches the airfoil divides, part of it going over the upper airfoil surface and part of it going below the airfoil surface. Bernoullis theorem would indicate that the airI-nearest. the upper=surface of the wing, which'is at a pressure less than that in the air at a distance from the wing has a velocity which is higher than that in the air stream at a'distance from the wing. On theother hand the velocity of the] air nearest the lower wing surface is less than that of the air stream. By further application of this theorem it will be appreciated that the pressure of the air passing-over the airfoil is less than the pressure of the air below the airfoil It'is thi's pressure diflerential which creates lift;

To go into further detail it is believed that such a condition as outlined above lies -in the assumption that a circulation of air exists that its leading edge is pointe about the airfoiL' Fro'mdemonstrations and experiments it has been shown, as a fact, that when air starts 'to move past the airfoil there is formed; along the trailing-edge a succession ofsmall vortices: which break off and ref main in the air as the airfoil passes. These trailing edge vortices, it is'assumed, setup a counter circulation around the wing which increases in strength untilthe flow off the trailingedge is smooth. This efiect takes 'place within a'comparatively small amount of timeand the full lift ofthe airfoil is developed very quickly-after the airfoil begins to move.

Assuming that'an airfoil is o'sitioned so d towards the left as shown in Figure 3, .such a counter ,circulation of air, asthat described above, is

' directed in a clockwise direction. Now this 7 counter a1r current, as it passes over the lowor surface of the airfoil, will'be opposite in direction. to the air flowing over the lower surface, caused by the movement of the air,-

l' foil, and hence will decrease its velocity with a consequent pressure rise; On the other hand as the: counter current of air passes -'around the leading edge and over the upper It is, the purpose of surface of; the airfoil its direction will be .coincident with-that of the airflowing over I this surface and it will t'endto add to or .build up the velocity of-this air with a-consequent decrease in pressure upon the upper invention, among build rent. able vanes-such as have been. shown are em- Besides increasing the pressure upon the lowthe generated air, caused by the rotation of the blade, to be given aconsiderable velocity initial position.

other objects as will be pointed out, make use of this theory as outlined above and to iapior strengthen the-counter air curorder to accomplish this the rotatthe opening 9.

Now as the .blade 10a is rota-ted from thepositiondescribed it moves downwardly and its front face, that is the face adjacent to the leading edgeof the airfoil, is in contact with the air flowing over the lower ailfoil' surface.

er surface, this results in deflectmg some of thisair stream into the interior of the airfoil and moreover createsa curre'ntor flow of air through the airfoil itself. As is well known centrifugal force will-cause the deflected and 1 as the blade 10a moves towards the leading edge and within the airfoil. This c'ircula- I tion of air within the airfoil is continued and because of the shape of the airfoil itself and l the cont-inued'rotation of 'the blade-willbe sweptv through the interior and ejected'or deflected'through the-righthand side of the opening 9 as the blade 1011 again assumes its It -.;will be observed that the direction of. this'air current flowing through the airfoil is clockwise and the same as the counter cur' rent of air set up by the trailing edge vortic'es. i

As this air is'ejected from theright of the openings 9, itis commingled with the circu-' latory counter current flowing around the airfoil and. the velocity of the latter i'sbuilt up due to the addition ofthe air expelled from within the airfoil as the blade descends.

The counter circulatory current of 'air flowmg over the lower surface of the airfoil, it

-will-be appreciated, has hadits'velocity-com. 1

siderablyincreased and as this meets the air stream flowing over the lower surface, in an opposite direction'to it, the veloci ofv the 1 latter will be decreased. This resu tsin-an'; increase of pressure upon the underside of the airfoil which exceeds the-amount possible to be attained without the use'ofthe vane element s. i

Now as this circulatory counter current of increased velocity passes-around thelea'ding edge of the airfoiland over its upper surface,"

it is directedin' a path substantiallyc0i n i'- V dent with the air stream flowing over the upper surface and the velocity of this air stream is built up with a consequent greater restriction of pressure on the upper surface. 5 Hence it will become apparent that by the use of the vane elements, as described, the pressure upon the lower surface of the airfoil will be considerably increased, while that upon the upper surface will be decreased. As it is apparent the result of this enlarged pressure differential will create an increased lift factor.

Besides generating an increased counter current having a circulatory flow around the airfoil, the invention intends to make use of the inner surfaces of the airfoil as well as the outer surfaces for lifting effects. It has already been mentioned that an air current of considerable velocity is circulated through.

0 the interior of the airfoil due to the rotation of the, blades forming each vane element. The velocity and pressure of this air is not only due to that deflected from the lower air stream by reason of it impinging against each 5 blade as it starts to ascend into the interior of the airfoil, but is also caused by air currentto exist between the upper exterior surface of the airfoil and the upper interior surface of the airfoil. As a consequence, an increased lift effect is provided for the airfoil and the interior surface as well as the exterior sur- 0 face will be utilized.

It has been mentioned that the blade elements are rotated at a suitable speed. Such a speed is dependent upon such factors as the size'of the airfoil, the area ofthe vanes, and

5 also'upon their number. While the vanes have been disclosed as being circular in shape, it will be appreciated that any other geometrical shape desired may be given to them without departing from the spirit of the ino vention or the scope of the appended claims.

Likewise it will be appreciated that the invention is not limited to the number of blades formed upon each blade element. For instance a single vane may be employed.

5 It will be appreciated that the invention is of great advantage in increasing the lift of an airplane, being particularly useful in taking off and landing. The power unit 14 is actuated so as to rotate the vahe elements as 0 described with the result that a counter circulatory airflow and an airflow within the interior of the airfoil are set up. This will greatly increase the lift coefficient at all angles of attack, and hence will allow the plane to be taken off within a relatively small space and to he landed at relatively low speed and within a small area.

While the plane is flying and it is no longer desired to rotate the vane elements, the actuation of the power unit is arrested and the shafts 11 may be unclutched therefrom. It should be noted that either or both sets of vane elements may be unclutched from the power unit and hence either or both of them ma be driven as desired.

, he pressure of the'air stream passing below the lower wing surfaces will maintain the vanes in closed position as shown in Figure 1, and the airfoil will function similar to any conventional wing. The reason for constructing the vane elements so that when they are in closed position they are flush with the lower surface, will now become apparent. By this construction parasitic resistance due to their projection below the airfoil surface is prevented. Although the bearings 14 have been shown as extending below the lower wing surface, it will be appreciated that these may be so constructed as to be substantially flush therewith.

While the advantages derived from this construction have been outlined in connection with the landing and the taking off of airplanes, and are of particular value in these instances, it will be undersood that they will be effective while the plane is flying 1n the air. Such a use of the vane elements is of advantage in pulling an airplane out of a stall, a dive, or a spin.

As is well known, there exists upon the wng tips of an airplane, a whirl or vortex, which creates an uneven distribution of pressure over the wing surfaces near thetips, in-

creases the drag of the airfoil and in general decreases the stabilit of the airplane. Attempts have been madi; to ameliorate this condition by varying the shape of the wing tip. As a consequence, it has been discovered that an elliptical tipped wing gives the best results, but these are not highly satisfactory. By suitably positioning a series of vane elements upon the wing tips, either as shown or so that the axis of rotation is perpendicular to the longitudinal plane axis or angularly disposed thereto, these aircurrents flowing over and under the wing tips could be straightened out and. hence an even distribution of the pressure over this area would be procured with a decrease in the drag of the airfoil.

In Figure 2 the invention is embodied in an auxiliary airfoil adapted to be mounted below the main airfoil of an airplane, one such auxiliary airfoil being positioned. on each semi-wing span. Here a cabin plane having a fuselage 1 and an airfoil 2 is provided with an auxiliary airfoil 15. The fuselags of the plane is provided with the usual wind shield and supporting structure therefor as indicated by the reference numeral 16.

' Each auxiliary wing '15 is provided with 4 a set of vane elements such as that described. These vane elements are actuated similarly to those shown in Figure 1. Under each semi- 5 span of the main airfoil 2' the auxiliary wing is mounted b means of suitable supports or braces 17 WhlCll may be secured to the main airfoil 2' or to the fuselage'itself to both of these structures. V

Each auxiliaryairfoil is positioned at such a distance below the main airfoil 2 that substantially no interference with the'air cur- ,rent passing under the lower surface of the airfoil 2- is created. As is well known, such 15 a distanceisidepe'ndent upon, the gap/cord ratio giving the best results and it may be gecreased by positively staggering the airoils.

. In such construction it will be appreciated l that the main airfoil 2' may also be provided with vane elements such as shownin' connection with the airfoil2 in Figures 1 and 3.

By the structure employed in Fi ure 2,-

construction of biplanes or triplanes aving a smaller wing area is permitted. Biplane 1 and triplane construction is. employed where it is found impractical, because of the wing area required, to embody an airplane design in a monoplane design. By'the use of the 0 auxiliary airfoils it will be appreciated that the wing area ofsuch a plane and consequently its weight, could be considerably reduced while its lift factor would be greatly increased. 'In the construction shown in Fig-, 5 ure 2 it will be apparent that both the main wing 2'.and the auxiliary wing willfunc tion ina manner similar to that described in the embodiment of the invention disclosed in Figures 1, 3 and 4. Y

- Units such as an auxiliary airfoil 15 employing the present invention may be positioned at various points on the anIincreased-lift is desirable.

It may be possible that the lift effect obtained' by the present invention is due to the plane where pressure created by centrifugal action of the vanes or impellers, which exerts a pressureupwardly against the interior of the wing tion of the device, it will be appreciated from o the foregoing description that 'I have provided amethod and means for'greatlyincreas ing the lifting powers of airfoils. Such construction as that'disclosed .will allow a short distance take off for aplane and a-relatively a small landing area besides having many other surfaceand also in a general opposite direc- 'advanta' eous effects which result from the benefit 0 increasing the lift of airfoils.

' 'While I have shown and described the preferred embodiment of m invention, I wish it to be understood that do not confine myself to the precise details of construction herein set forth, by way of-illustration, as

it is apparent that many changes and variations may be made therein, by those skilled in'the art, withoutdeparting from the spirit ofthe invention, or exc'eedin g the scope of the appended claims. v

I claim;

1.: An airfoil having a plurality of openings within its lower surface, disk-hke nnpellers rotatably mounted within said openings', each of said impellers being so .con-

,structed that when it is in the position to close the opening within which it is mounted it lies substantially flush with the surfacing material of the airfoil.

2. An airfoil having a plurality of recesses formed upon its lower surface, rotary impel-' lers substantially the same size as said recesses rotatably mounted therein, each of sald impellers being so constructed as to lie substantially flush with the surfacing material of said airfoil when it is in position to closeits opening, and'means for rotating said impellers.

3. In an airfoil, the lower surface thereof being provided with a recess, a shaft extend ing through said recess,-a disk-like impeller mounted upon said shaft and'positioned within said recess, and means connected to said shaft for rotating it and said impeller. I 4. An airplane wing having a plurality of openings within its lower surface, said openings being positioned in sets upon opposite semi-spans of the wing, a s'haftadapted to extend through each set of openings, impellers mounted upon said shaft and positioned within each opening, and means connected to each shaft for rotating the same and -the impellers mounted thereon.

5. In an airplane a plurality-of auxiliary adapted to be mounted below the main airfoil of said airplane, each of said auxiliary airfoils being provided with a plurality of openings formed upon their bottom surface, and vane elements rotatably mounted within each of said elements.

6. An auxiliary airfoil 'for-an airplane adapted to be mounted below a wing of said airplane, said auxiliary airfoil being provided' with a plurality of openings upon its lower surface, vane elements rotatably mounted within said openings, said vane ele-- ments being so constructed as to lie substantially flush with the lower surface of said auxiliary airfoil when the vane elements are in position to close said openings.

7. In an airplane anauxiliary wing therefor adapted to be positioned belowa main airfoils therefor, said auxiliary airfoils wing, said auxiliary wing having an airfoil section and provided with an opening upon its bottom surface, an impeller rotatably mounted within said opening, and power driven means upon the airplane for rotating said impeller.

8. In an airplane an auxiliary wing therefor adapted to be positioned below the main wing, said auxiliary wing having an airfoil sectlon and provided with a plurality of openings upon its lower surface, vane elements adapted to be rotated about a horizontal axis mounted within said openings and power driven means upon said airplane for rotating said vane elements.

9. An auxiliary wing for an airplane having an airfoil section and provided with a plurality of recesses formed upon its bottom surface, vane elements rotatably mounted Within said recesses, said elements being adapted to rotate about a horizontal axis, perpendicular to the path of travel of the airplane through an are greater than 360.

In testimony whereof I aflix my sigr ature.

TRIAN BERBECK. 

